Lysophospholipids is the collective term for phospholipids having a single acyl group. Compared to diacylphospholipids that constitute cell membranes, lysophospholipids are less hydrophobic and have such a property that they can easily become free from the cell membranes. Acting as signal molecules between cells or membranes, some lysophospholipids have been shown to have an important role in vivo and it has heretofore been known that phospholipids in biomembranes are hydrolyzed to produce lysophospholipids when inflammatory reactions such as tissue damage take place (Patent Document 1). Lysophosphatidylserine (LysoPS) which is a kind of lysophospholipids is known to be involved in acute inflammations due to degranulation of mast cells (Non-Patent Documents 1 and 2). As LysoPS receptors, the G protein coupled receptors GPR34, P2Y10, A630033H20Rik and GPR174 have been identified (Non-Patent Document 3) and among these, GPR34, P2Y10, and GPR174 are referred to as LPS1, LPS2, and LPS3 (Non-Patent Document 4). Among these, LPS1 has been reported to be involved in signaling for inducing or enhancing the degranulation reaction of mast cells so that it can be a target for the treatment of allergic diseases and chronic inflammatory diseases (Patent Documents 1 and 2). It is also known that a certain lysophosphatidylserine derivative (lysophosphatidylthreonine) is a potent promoter of the degranulation reaction of mast cells (Patent Documents 3 and 4).
Methods for screening compounds useful as therapeutics for autoimmunity and the discovery of lysophosphatidylserine and derivatives thereof by such screening methods have been reported (Patent Document 5). Autoimmune diseases is the collective term for diseases that become symptomatic when an immune system which is normally a defense mechanism against foreign bodies responds excessively and even attacks normal cells or tissues of the self; autoimmune diseases are roughly divided into systemic autoimmune diseases that affect the whole body and organ-specific diseases that affect only certain organs. In general, autoimmune diseases often end up with chronic or refractory diseases and some of them are cited by the Ministry of Health, Labour and Welfare in the List of Diseases under Intensive Study. Much research has been made on the methods for treating autoimmune diseases and the methods reported so far include a method for treating chronic inflammation due to autoimmune disease using a cytokine specific antibody involved in inflammation (Patent Document 6) and a therapeutic method for disease that involves neutralizing a pathogenic autoantibody (Patent Document 7). However, much is left unraveled about the cause of autoimmune disease and no effective therapy has yet been established for many autoimmune diseases. To treat autoimmune disease, medications that suppress the immune system or anti-inflammatory drugs that mitigate inflammation (steroids or non-steroids) are being used as drugs of first choice.